The invention relates to an operating mechanism of a molded case low-voltage electrical circuit breaker comprising:
a latch articulated on a fixed spindle and having a cam surface; PA1 a toggle formed by a toggle spindle, a first lever linked on the one hand to the movable contact and on the other hand to the toggle spindle, and a second lever articulated on the one hand on the latch and on the other hand on the toggle spindle; PA1 a spring attached on the one hand to the toggle spindle and on the other hand to the handle; PA1 a lock designed to cooperate with the latch to hold the latter in the locked position; and PA1 a cam-follower roller actuated by the handle and designed to cooperate with the cam surface of the latch to move the latch to the locked position, the handle being able to move to three distinct positions, a closed position in which the spring urges the toggle to an extension position, a manual opening and resetting position where the spring urges the toggle to a broken position wherein latch being in the locked position, and a tripped position in which the latch is unlocked and the toggle broken.
A circuit breaker of the kind mentioned above, for example described in U.S. Pat. No. 4,710,738, comprises an operating handle whose pivoting in either direction causes opening and closing of the circuit breaker contacts. When a fault occurs, notably an over-load or short-circuit, the contacts open automatically due to the action of a trip device and the handle moves to an intermediate tripped position between the closed position and the open position. To reset the circuit breaker, the handle has to be moved beyond the open position to a reset position where the latch is moved to the locking position. This reset position is an unstable position and the handle automatically returns to the open position when released. The latch being locked, the circuit breaker can again be reclosed and opened by a manual operation, or open automatically when a fault occurs. Nuisance unlocking of the latch may occur when the circuit breaker is open. Unlocking naturally causes the mechanism to be disarmed and the handle to return to the tripped position. Nuisance unloading can result from a wrong control or a mechanical action on the circuit breaker, or for any other reason, and a second resetting operation is necessary before the circuit breaker can be reclosed. Operating malfunctions of this kind can be bothersome, notably when remote controls are involved.
The object of the present invention is to achieve a circuit breaker mechanism holding the handle and latch in the loaded position, when nuisance tripping occurs.